Lamblet M, Verneuil E, Vilmin T, Buguin A, Silberzan P, Léger L
Physico-Chimie Curie, UMR 168, CNRS-Institut Curie, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France.
Langmuir. 2007 Jun 19;23(13):6966-74. doi: 10.1021/la063104h. Epub 2007 May 19.
Adhesion at polydimethylsiloxane (PDMS)-acrylic adhesive interfaces is shown to be enhanced through micropatterning of the PDMS substrate. By varying the geometry of the patterns (groves and hexagonal arrays of pillars of micrometer sizes, obtained through soft lithography techniques) and comparing rigid and deformable substrates, the respective roles of the geometry and the size and flexibility of the pattern features on the level of adhesion have been analyzed. For cylindrical pillars, two regimes are clearly identified: for a relatively low aspect ratio (h/r < 3, with h and r, respectively, the height and the radius of the pillars), soft patterned substrates are more efficient than rigid ones at increasing adhesion, pointing out the role of the elastic energy associated with the deformation of the pattern that is lost when the adhesive detaches from the substrate. Using scaling laws, the predominant contribution to that elastic energy can be further identified: deformation of the substrate underlying the pillars for h/r < 1.6 or bending of the pillars for h/r > 1.6.; for a high aspect ratio (h/r > 3), only rigid patterned substrates enhance adhesion, then the only possible contribution to energy dissipation comes from the enhanced viscoelastic losses associated with the pattern that induce modifications of the strain field within the adhesive layer. Soft, high aspect ratio patterns lose their efficiency even if still bent under the effect of the peel forces. This is because when bent, some of the pillars touch each other and remain stuck together, lying flat on the surface after the passage of the peel front. The bending elastic energy of the pillars (which is still lost) is then balanced by the corresponding gain in surface energy of the substrate in the peeled region. These systematic experiments demonstrate that the ability of the patterned surface to be deformed plays a crucial role in enhancing adhesion and allow us to propose a way to fine tune the level of adhesion at PDMS-acrylic adhesive interfaces, independently of the chemistry of the adhesive.
通过对聚二甲基硅氧烷（PDMS）基底进行微图案化，可增强PDMS与丙烯酸粘合剂界面的粘附力。通过改变图案的几何形状（通过软光刻技术获得的微米尺寸的沟槽和柱状六边形阵列），并比较刚性和可变形基底，分析了图案特征的几何形状、尺寸和柔韧性对粘附力水平的各自作用。对于圆柱形柱子，可明确识别出两种情况：对于相对较低的纵横比（h/r < 3，其中h和r分别为柱子的高度和半径），软图案化基底在增加粘附力方面比刚性基底更有效，这表明了与图案变形相关的弹性能量的作用，当粘合剂从基底分离时，该弹性能量会损失。使用比例定律，可以进一步确定对该弹性能量的主要贡献：对于h/r < 1.6，柱子下方基底的变形；对于h/r > 1.6，柱子的弯曲；对于高纵横比（h/r > 3），只有刚性图案化基底能增强粘附力，此时能量耗散的唯一可能贡献来自与图案相关的增强的粘弹性损耗，这会引起粘合剂层内应变场的改变。即使在剥离力的作用下仍会弯曲，软的、高纵横比的图案也会失去其有效性。这是因为弯曲时，一些柱子会相互接触并粘在一起，在剥离前沿通过后平躺在表面上。柱子的弯曲弹性能量（仍然会损失）随后会被剥离区域基底表面能的相应增加所平衡。这些系统实验表明，图案化表面的变形能力在增强粘附力方面起着关键作用，并使我们能够提出一种方法来微调PDMS - 丙烯酸粘合剂界面的粘附力水平，而与粘合剂的化学性质无关。
